* {
    /* 去除页面内外边距 */
    padding: 0;
    margin: 0;
}

body {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background-color: #000000;
}

html::after {
    content: "By Ghost.";
    position: absolute;
    bottom: 10px;
    color: cyan;
    right: 10px;
    z-index: 15;
}

a {
    position: relative;
    width: 400px;
    height: 80px;
    line-height: 80px;
    text-align: center;
    text-decoration: none;
    text-transform: uppercase;
    font-size: 24px;
    /* 圆角属性 */
    border-radius: 50px;
    color: #fff;
    /* 背景颜色 */
    background-image: linear-gradient(to right, #03a9f4, #f441a5, #ffeb3b, #09a8f4);
    background-size: 400%;
}

a:hover::before,
a:hover {
    /*            名称  完成时间   动画速度曲线      延时   动画播放次数      轮流反向   不播放应用到元素状态 */
    /* animation: name duration timing-function delay iteration-count direction fill-mode; */
    /*          名称 时间  不限次     */
    animation: sun 8s infinite forwards;

}

@keyframes sun {
    100% {
        background-position: -400%, 400%;
    }
}

a::before {
    border: orange 1px solid;
    content: "";
    position: absolute;

    top: -3px;
    bottom: -3px;
    left: -3px;
    right: -3px;
    border-radius: 50px;
    background-image: linear-gradient(to right, #03a9f4, #f441a5, #ffeb3b, #09a8f4);
    background-size: 400%;
    z-index: -1;
    filter: blur(10px);
}